Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

5.5.2Unit 5. Transition Metals and Organic Nitrogen Chemistry

Primary Aliphatic Amines — IAL Edexcel Linear (Chemistry) Revision Notes & Topical Questions

5 min read 5 parts Lesson 32 of 43 Unit quiz

📚 IAL Edexcel Linear (Chemistry) Hub / Topical Revision
🩺
100% Curriculum Specification Match Lesson Doctor Verified
The only platform with 100% curriculum specification match and verified interactive question banks.
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
0%read

Part 1 of 5Preparation

1
Heat a halogenoalkane with excess ammonia dissolved in ethanol in a sealed tube.
2
CH₃CH₂Br + 2NH₃ → CH₃CH₂NH₂ + NH₄Br, where the excess ammonia limits further substitution.
3
Alternatively, convert a halogenoalkane to a nitrile using KCN in ethanol, which adds one carbon to the chain.
4
Reduce the nitrile with LiAlH₄ in dry ether, or with hydrogen and a nickel catalyst: CH₃CN + 4[H] → CH₃CH₂NH₂.
5
Separate the amine from the mixture, remembering that excess halogenoalkane would give secondary and tertiary amines.

Part 2 of 5Amines as Bases

Why basic
  • Why basic The lone pair on nitrogen accepts a proton from an acid.
Reaction with acid
  • Reaction with acid CH₃CH₂NH₂ + HCl → CH₃CH₂NH₃⁺Cl⁻, a salt called an alkylammonium chloride.
Strength
  • Strength Alkyl groups donate electrons, increasing the electron density on nitrogen, so primary amines are stronger bases than ammonia.
Reversal
  • Reversal Adding sodium hydroxide to the salt releases the free amine, CH₃CH₂NH₃⁺ + OH⁻ → CH₃CH₂NH₂ + H₂O.
Ammonia comparison
  • Ammonia comparison Ammonia, the parent compound, is a weaker base because it has no electron-donating alkyl group on the nitrogen atom.
Test
  • Test Ethylamine-type compounds dissolved in water give an alkaline solution, which turns red litmus paper blue.

Part 3 of 5Amines as Nucleophiles

Amines as Nucleophiles
With acyl chlorides
  • With acyl chlorides CH₃COCl + 2CH₃NH₂ → CH₃CONHCH₃ + CH₃NH₃⁺Cl⁻, forming an N-substituted amide.
With halogenoalkanes
  • With halogenoalkanes Further substitution gives secondary and tertiary amines and then a quaternary ammonium salt.
With copper(II)
  • With copper(II) Amines act as ligands, replacing water in [Cu(H₂O)₆]²⁺ to give a deep blue solution.

Part 4 of 5Worked Example

Question Name the product formed when bromoethane reacts with excess ammonia in ethanol, and give the equation.

  1. Ammonia replaces bromine, a nucleophilic substitution.
  2. Two moles of ammonia are usedone forms the amine and one takes up HBr.

Answer

  • CH₃CH₂Br + 2NH₃ → CH₃CH₂NH₂ + NH₄Br;
    • the product is ethylamine

Part 5 of 5Exam Checklist & Tips

5.5.2 – Key Points for the Exam

  • Nucleophile An electron-pair donor.
  • Primary amine An amine with one organic group on nitrogen.
  • Alkylammonium salt The ionic product of an amine and an acid.
  • Nitrile A compound containing -C≡N.

Common Mistakes

  • Using limited ammonia and expecting a pure primary amine.
  • Forgetting that the nitrile route adds a carbon.
  • Writing the salt without the positive charge on nitrogen.
  • Saying that amines are acids.

Last updated:

\n